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半透发光式与逆反射式指路标志视认效果对比分析 被引量:2
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作者 胡江碧 陈丽 +1 位作者 孙淑娅 王荣华 《安全与环境学报》 CAS CSCD 北大核心 2020年第3期1013-1020,共8页
为保证隧道内驾驶员对指路标志的安全视认,分析隧道照明光环境、标志特性对驾驶员视认距离的影响,营造了隧道中间段5种色温、3种亮度照明光环境,随机选取了20名小客车驾驶员进行半透发光式与逆反射式指路标志的视认试验。结果表明:隧道... 为保证隧道内驾驶员对指路标志的安全视认,分析隧道照明光环境、标志特性对驾驶员视认距离的影响,营造了隧道中间段5种色温、3种亮度照明光环境,随机选取了20名小客车驾驶员进行半透发光式与逆反射式指路标志的视认试验。结果表明:隧道内半透发光式指路标志的视认距离明显优于逆反射式指路标志,且半透发光式指路标志的最佳字体照度范围为3 000~3 500 lx;在最佳的背景光环境条件下,半透发光式指路标志与字高53 cm,笔画在5画以下、5~10画及10画以上的逆反射式指路标志达到相同的视认效果时,字高分别缩减了35. 85%、30. 19%和24. 53%。半透发光式指路标志的应用可提高隧道内指路标志的视认距离,并能减少交通事故的发生,可为以后隧道内交通标志的改进与创新提供理论支撑。 展开更多
关键词 安全工程 隧道内照明光环境 反射路标志 半透发光式路标志 字体照度 视认距离
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一种单指无内反射结构换能器的频谱分析
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作者 曹亮 傅金桥 肖燕 《压电与声光》 CSCD 北大核心 1996年第1期1-5,共5页
采用叉指换能器的脉冲响应模型,建立了三指群和四指群分组单指无内反射结构换能器的脉冲响应解析表达式,并在此基础上通过付氏级数分解,分析了该结构的频谱特性,最后给出了实验验证结果.
关键词 声表面波 换能器 反射 频谱分析
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Analysis of Physical Quantities and Radar Parameters about Hail Shooting and Heavy Convective Rainfall
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作者 陈金敏 刁秀广 《Agricultural Science & Technology》 CAS 2012年第11期2434-2437,2441,共5页
[Objective] The paper is to analyze physical quantities and radar parameter of hail shooting and heavy convective rainfall weather. [Method] Using radar data of Jinan station during 2002 and 2008, combined with soundi... [Objective] The paper is to analyze physical quantities and radar parameter of hail shooting and heavy convective rainfall weather. [Method] Using radar data of Jinan station during 2002 and 2008, combined with sounding data, the physical quantities and radar parameter of hail shooting and heavy convective rainfall weather are compared and analyzed. [Result] The smaller Sl is conducive to the generation of hail weather. When K〉 35 ~C, the probability for occurrence of heavy rainfall weather is significantly increased; when K〈20 ^(3, the probability for occurrence of heavy rainfall weather is significantly decreased. When CAPE value is greater than 1 500 J/KG, the probability for occurrence of hail weather is significantly decreased, while the probability for occurrence of heavy rainfall weather is significantly in- creased. The possibility for occurrence of hail monomer is small when the wind shear is less than 5 m/s; and it is large while wind shear is greater than 20 m/s. The radar forecasting indexes of hail monomer is as follows: VIL value reaches 35 kg/m2 (May), 43 kg/m2 (June and July), the monomer height is greater than 9 km, the maximum reflectivity factor is larger than 60 dBz, strong center height reaches 3.3 km (May), 4.3 km (June) and 5.5 km (July); VlL value of heavy rainfall monomer generally is below 25 kg/m2. [Conclusion] The paper provides basis form prediction of hail and heavy rainfall. 展开更多
关键词 HAIL Heavy convective rainfall VIL Weather radar parameter
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超小型声表面波谐振器 被引量:1
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作者 仇钢 章德 何小悦 《应用声学》 CSCD 北大核心 2003年第6期1-5,共5页
传统声表面波谐振器中的指条反射阵占据了器件的大部分尺寸。由于剪切横波(SH wave)在材料基片的自由端面反射时不产生模式转换,因此可望利用自由端面来代替SH型声表面波谐振器中的指条反射阵,实现超小型低损耗的新型声表面波谐振器。... 传统声表面波谐振器中的指条反射阵占据了器件的大部分尺寸。由于剪切横波(SH wave)在材料基片的自由端面反射时不产生模式转换,因此可望利用自由端面来代替SH型声表面波谐振器中的指条反射阵,实现超小型低损耗的新型声表面波谐振器。本文首先用COM理论对新结构的谐振器进行了讨论,并且在实验上实现了120MHz至440MHz的几个单端谐振器(ST36°石英基片),其插入损耗从0.87dB至1.29dB,面积缩小到传统谐振器的50%至25%。 展开更多
关键词 声表面波谐振器 反射 剪切横波 COM理论 滤波器 通信系统
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Predicting Grain Yield and Protein Content in Winter Wheat at Different N Supply Levels Using Canopy Reflectance Spectra 被引量:17
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作者 XUE Li-Hong CAO Wei-Xing YANG Lin-Zhang 《Pedosphere》 SCIE CAS CSCD 2007年第5期646-653,共8页
A field experiment using a split-plot randomized complete block design with three replications was carried out to determine relationships between spectral indices and wheat grain yield (GY), to compare the performan... A field experiment using a split-plot randomized complete block design with three replications was carried out to determine relationships between spectral indices and wheat grain yield (GY), to compare the performance of four vegetation indices (VIs) for GY prediction, and to study the feasibility of VI to estimate grain protein content (GPC) in winter wheat. Two typical winter wheat (Triticum aestivum L.) cultivars 'Xuzhou 26' (high protein content) and 'Huaimai 18' (low protein content) were used as the main plot treatments and four N rates, i.e., 0, 120, 210, and 300 kg N ha^-1, as the sub-plot treatments. Increasing soil N supply significantly increased GY and GPC (P ≤ 0.05). For the two cultivars combined, significant and positive correlations were found between four VIs and GY, with the strongest relationship observed when using the green ratio vegetation index (GRVI) at mid-filling. Cumulative VI estimates improved yield predictions substantially, with the best interval being heading to maturity stage. Similar results were found between VI and grain protein yield. However, when using cumulative VI, GPC showed no significant improvement. The strong relationship between leaf N status and GPC (R2 =0.9144 for 'Xuzhou 26' and R2 = 0.8285 for 'Huaimai 18') indicated that canopy spectra could be used to predict GPC. The strong fit between estimated and observed GPC (R2 = 0.7939) indicated that remote sensing techniques were potentially useful predictors of grain protein content and quality in wheat. 展开更多
关键词 grain protein content grain yield soil N supply vegetation index WHEAT
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Relationship of 2 100-2 300 nm Spectral Characteristics of Wheat Canopy to Leaf Area Index and Leaf N as Affected by Leaf Water Content 被引量:10
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作者 ZHAO Chun-Jiang WANG Ji-Hua +2 位作者 LIU Liang-Yun HUANG Wen-Jiang ZHOU Qi-Fa 《Pedosphere》 SCIE CAS CSCD 2006年第3期333-338,共6页
The effects of leaf water status in a wheat canopy on the accuracy of estimating leaf area index (LAI) and N were determined in this study using extracted spectral characteristics in the 2 000-2 300 nm region of the s... The effects of leaf water status in a wheat canopy on the accuracy of estimating leaf area index (LAI) and N were determined in this study using extracted spectral characteristics in the 2 000-2 300 nm region of the short wave infrared (SWI) band. A newly defined spectral index, relative adsorptive index in the 2000-2300 nm region (RAI2000-2300), which can be calculated by RAI2000-2300 = (R2224 - R2054) (R2224 + R2054)-1 with R being the reflectance at 2224 or 2054 nm, was utilized. This spectral index, RAI2000-2300, was significantly correlated (P < 0.01) with green LAI and leaf N concentration and proved to be potentially valuable for monitoring plant green LAI and leaf N at the field canopy scale. Moreover, plant LAI could be monitored more easily and more successfully than plant leaf N. The study also showed that leaf water had a strong masking effect on the 2 000-2 300 nm spectral characteristics and both the coefficient between RAI2000-2300 and green LAI and that between RAI2000-2300 and leaf N content decreased as leaf water content increased. 展开更多
关键词 leaf area index NITROGEN plant water status reflectance Triticum aestivum L.
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低插损高频SAW滤波器的研究 被引量:1
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作者 王巍 周杨春 +3 位作者 王方 谭纪伟 滕洪菠 李俊峰 《压电与声光》 CAS 北大核心 2022年第2期180-186,共7页
采用单层膜、梯形结构基于128°YX-LiNbO_(3)材料研究了Al电极厚度、叉指占空比、反射栅周期、拓扑结构对插损、带外抑制和矩形度的影响。为了降低带内波动和插入损耗,该文设计了一种叉指换能器(IDT)型反射栅结构,该结构对采取优化... 采用单层膜、梯形结构基于128°YX-LiNbO_(3)材料研究了Al电极厚度、叉指占空比、反射栅周期、拓扑结构对插损、带外抑制和矩形度的影响。为了降低带内波动和插入损耗,该文设计了一种叉指换能器(IDT)型反射栅结构,该结构对采取优化措施前后谐振器的带内最大尖峰损耗分别降低了8.84%和0.55%。最后采用此反射栅结构设计了一款低插损高频声表面波(SAW)滤波器,有限元仿真结果表明,该滤波器的中心频率为2.5205 GHz,插入损耗为-0.50212 dB,带外抑制大于30 dB,-3 dB损耗带宽大于98 MHz。 展开更多
关键词 占空比 声表面波(SAW)滤波器 换能器(IDT)型反射 电极厚度 “T+π”型拓扑结构
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Modulation by anti-oketsu formulations in Kampo medicine of human arterial stiffness
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作者 Hiroyasu Satoh 《Traditional Medicine Research》 2017年第3期130-138,共9页
Objective:In traditional herbal medicine(Kampo medicine in Japan),'sho'is diagnosed by the traditional assessments of clinical conditions.Among a variety of the shos,there is an'oketsu'syndrome,which i... Objective:In traditional herbal medicine(Kampo medicine in Japan),'sho'is diagnosed by the traditional assessments of clinical conditions.Among a variety of the shos,there is an'oketsu'syndrome,which is a stagnation and disturbance of microcirculation.The prompt effects of four anti-oketsu formulations in Kampo medicine on cardiovascular functions were compared in oketsu and non-oketsu persons.Methods:The arterial pulse wave from radial artery is formed by the combination with ejection and reflection pulses.An augmentation index(AI),a ration of the ejection and reflection pulses,indicates a degree of arteriosclerosis.For both seventy-six students with oketsu and thirty-seven students with non-oketsu,Kampo formulations overcoming oketsu of Tokishakuyakusan(TS,Dang-Gui-Shao-Yao-San),Kamishoyosan(KS,Jia-Wei-Xiao-Yao-San),Keisibukuryogan(KB,Gui-Zhi-Fu-Ling-Wan)and Tokakujokito(TJ,Tao-He-Cheng-Qi-Tang)were taken once,and then,the cardiovascular functions including blood pressure,heart rate,central arterial blood pressure(CBP)and AI were examined for 60 min.Results:At 40-60 min after an intake,these formulations decreased the AI almost by 6-18%(n=76),by 18.3±3.1%(P<0.01,n=15)with TJ.Simultaneously,the CBP was reduced by 9.0±1.8%(P<0.05,n=23)with KS and by 9.1±2.0%(P<0.05,n=15)with TJ.On the other hands,non-oketsu group had less or no effect by any kinds of the formulations.Conclusion:The anti-oketsu formulations can exert the ameliorative action for oketsu persons via decreasing AI and CBP. 展开更多
关键词 Kampo medicine Sho Oketsu Disturbances of microcirculation Augmentation index Central arterial blood pressure
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在伊斯坦布尔逛“大市场”
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作者 杨曼苏 《世界知识》 北大核心 1989年第5期27-27,共1页
到过土耳其伊斯坦布尔的人,都爱去逛逛著名的“大市场”。“大市场”是西方人的称谓,土语叫“卡帕勒恰尔市”,意为“室内市场”,它设在伊斯坦布尔“加洛鲁”闹市区一座有五六百年历史的古建筑之内,附近是世界闻名的伊斯坦布尔大学、圣... 到过土耳其伊斯坦布尔的人,都爱去逛逛著名的“大市场”。“大市场”是西方人的称谓,土语叫“卡帕勒恰尔市”,意为“室内市场”,它设在伊斯坦布尔“加洛鲁”闹市区一座有五六百年历史的古建筑之内,附近是世界闻名的伊斯坦布尔大学、圣索菲亚大教堂、蓝色清真寺和托普卡波皇宫。游人至此既可以游览名胜古迹,又可以去“大市场”选购合意的商品,因此这一带是伊斯坦布尔一个游客众多的热闹场所。“大市场”名符其实地大。它占地4.2万平方米,4000多个店铺分布在82条大小商业街道上。 展开更多
关键词 圣索菲亚大教堂 卡波 卡帕 世界闻名 托普 金项链 指反射 精密电子 示优 打主
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等待日出,等待花开(组诗)
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作者 吴俊 《草原》 2015年第8期68-69,共2页
白桦夜晚,团聚在星星周围雅克萨的雪悄悄铺了一层这是你降生后的寂静时刻白桦。
关键词 就这样 月光下 在远方 指反射 浪淘沙 想不起
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Matrix Rings over Reflexive Rings
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作者 Jeoung Soo Cheon Tai Keun Kwak Yang Lee 《Algebra Colloquium》 SCIE CSCD 2018年第3期459-474,共16页
The concept of reflexive property is introduced by Mason. This note concerns a ring-theoretic property of matrix rings over reflexive rings. We introduce the concept of weakly reflexive rings as a generalization of re... The concept of reflexive property is introduced by Mason. This note concerns a ring-theoretic property of matrix rings over reflexive rings. We introduce the concept of weakly reflexive rings as a generalization of reflexive rings. From any ring, we can construct weakly reflexive rings but not reflexive, using its lower nilradical. We study various useful properties of such rings in relation with ideals in matrix rings, showing that this new property is Morita invariant. We also investigate the weakly reflexive property of several sorts of ring extensions which have roles in ring theory. 展开更多
关键词 weakly reflexive ring reflexive ring power of ideal matrix ring ring of minimal order
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Energy exchange of an alpine grassland on the eastern Qinghai-Tibetan Plateau 被引量:9
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作者 尚伦宇 张宇 +1 位作者 吕世华 王少影 《Science Bulletin》 SCIE EI CAS CSCD 2015年第4期435-446,M0003,共13页
The seasonal variability in the surface energy exchange of an alpine grassland on the eastern Qinghai- Tibetan Plateau was investigated using eddy covariance measurements. Based on the change of air temperature and th... The seasonal variability in the surface energy exchange of an alpine grassland on the eastern Qinghai- Tibetan Plateau was investigated using eddy covariance measurements. Based on the change of air temperature and the seasonal distribution of precipitation, a winter season and wet season were identified, which were separated by transitional periods. The annual mean net radiation (Rn) was about 39 % of the annual mean solar radiation (Rs). Rn was relatively low during the winter season (21% of Rs) compared with the wet season (54 % of Rs), which can be explained by the difference in surface albedo and moisture condition between the two seasons. Annually, the main consumer of net radiation was latent heat flux (LE). During the winter season, sensible heat flux (H) was dominant because of the frozen soil condition and lack of precipita- tion. During the wet season, LE expended 66 % of Rn due to relatively high temperature and sufficient rainfall cou- pled with vegetation growth. Leaf area index (LAI) had important influence on energy partitioning during wet season. The high LAI due to high soil water content (θv) contributed to high surface conductance (go) and LE, and thus low Bowen ratio (β). LE was strongly controlled by Rn from June to August when gc and θv were high. During the transitional periods, H and LE were nearly equally parti- tioned in the energy balance. The results also suggested that the freeze-thaw condition of soil and the seasonal distribution of precipitation had important impacts on the energy exchange in this alpine grassland. 展开更多
关键词 Eddy covariance - Energy exchange Freeze-thaw condition Leaf area index Moisturecondition The eastern Qinghai-Tibetan Plateau
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Calibration of ASTER and ETM + Imagery Using Empirical Line Method——A Case Study of North-East of Hajjah, Yemen
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作者 ALI M. Qaid BASAVARAJAPPA H T +1 位作者 RAJENDRAN S ASHFAQ S A 《Geo-Spatial Information Science》 2009年第3期197-201,共5页
This study is aimed at using the Empirical Line Method (ELM) to eliminate atmospheric effects with respect to visible and near infrared bands of advanced spaceborne thermal emission and reflection radiometer (ASTER... This study is aimed at using the Empirical Line Method (ELM) to eliminate atmospheric effects with respect to visible and near infrared bands of advanced spaceborne thermal emission and reflection radiometer (ASTER) and enhanced thematic mapper plus (ETM+) data. Two targets (Amran limestone as light target and quartz-biotite-sericite-graphite schists as dark target), which were widely exposed and easy to identify in the imagery were selected. The accuracy of the atmospheric correction method was evaluated from three targets (vegetation cover, Amran limestone and Akbra shale) of the surface reflectance. Analytical spectral devices (ASD) FieldSpec3 was used to measure the spectra of target samples. ETM+ data were less influenced by the atmospheric effect when compared to ASTER data. Normalized differences vegetation indices (NDVI) displayed good results with reflectance data when compared with digital number (DN) data because it is highly sensitive to ground truth reflectance (GTR). Most of the differences observed before and after calibration of satellite images (ASTER and ETM+) were absorbed in the SWlR region. 展开更多
关键词 ELM ASTER ETM+ GTR FieldSpec3
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